xstr(1) 							   User Commands							   xstr(1)

NAME

       xstr - extract strings from C programs to implement shared strings

SYNOPSIS

       xstr -c filename [-v] [-l array]

       xstr [-l array]

       xstr filename [-v] [-l array]

DESCRIPTION

       xstr  maintains	a file called strings into which strings in component parts of a large program are hashed. These strings are replaced with
       references to this common area. This serves to implement shared constant strings, which are most useful if they are also read-only.

       The command:

	 example% xstr -c filename

       extracts the strings from the C source in name, replacing string references by expressions of the form &xstr[number] for  some  number.	An
       appropriate  declaration  of  xstr  is  prepended  to  the file.  The resulting C text is placed in the file x.c, to then be compiled.  The
       strings from this file are placed in the strings data base if they are not there already. Repeated strings and strings which  are  suffixes
       of existing strings do not cause changes to the data base.

       After  all components of a large program have been compiled, a file declaring the common xstr space called xs.c can be created by a command
       of the form:

	 example% xstr

       This xs.c file should then be compiled and loaded with the rest of the program.	If possible, the array can be made read-only (shared) sav-
       ing space and swap overhead.

       xstr can also be used on a single file.	A command:

       example% xstr filename

       creates files x.c and xs.c as before, without using or affecting any strings file in the same directory.

       It may be useful to run xstr after the C preprocessor if any macro definitions yield strings or if there is conditional code which contains
       strings which may not, in fact, be needed. xstr reads from the standard input when the  argument  `-'  is  given.  An  appropriate  command
       sequence for running xstr after the C preprocessor is:

	 example% cc -E name.c | xstr -c -
	 example% cc -c x.c
	 example% mv x.o name.o

       xstr does not touch the file strings unless new items are added; thus make(1S) can avoid remaking xs.o unless truly necessary.

OPTIONS

       -c filename	 Take C source text from filename.

       -v		 Verbose: display a progress report indicating where new or duplicate strings were found.

       -l array 	 Specify the named  array in program references to abstracted strings.	The default array name is xstr.

FILES

       strings	   data base of strings

       x.c	   massaged C source

       xs.c	   C source for definition of array "xstr*(rq

       /tmp/xs*    temp file when xstr filename doesn't touch strings

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       make(1S), attributes(5)

BUGS

       If a string is a suffix of another string in the data base, but the shorter string is seen first by xstr both strings will be placed in the
       data base, when just placing the longer one there would do.

NOTES

       Be aware that xstr indiscriminately replaces all strings with expressions of the form &xstr[number] regardless of the way  the  original  C
       code might have used the string.  For example, you will encounter a problem with  code that uses sizeof() to determine the length of a lit-
       eral string because xstr will replace the literal string with a pointer that most likely will have a different size than the  string's.	To
       circumvent this problem:

	   o	  use  strlen()  instead  of   sizeof();  note	that  sizeof() returns the size of the array (including the null byte at the end),
		  whereas strlen() doesn't count the null byte. The equivalent of sizeof("xxx") really is (strlen("xxx"))+1.

	   o	  use #define for operands of sizeof() and use the define'd version. xstr ignores #define statements.  Make sure you run  xstr	on
		  filename before you run it on the preprocessor.

       You will also encounter a problem when declaring an initialized character array of the form

	 char x[] = "xxx";

       xstr will replace  xxx with an expression of the form &xstr[number] which will not compile.  To circumvent this problem, use static char *x
       = "xxx" instead of static char x[] = "xxx".

SunOS 5.11							    14 Sep 1992 							   xstr(1)